Doing the deal on your real estate

A Realtor once told us we were unreasonable. Well, actually we've been told that a couple of times. But we know what we want and when we want it and this isn't our first rodeo, so....

We have a hard time with this dual agency thing.

Why do Realtors think that they can fairly represent both the buyer and the seller? We have completely different agendas now, don't we?
If they're looking after our best interests, how can they possible cut a good deal for the buyer? If say they can get an attractive price for your property, how can they turn around and tell the buyer that they can sell a low offer for them?

Are they all on Jeckell and Hyde juice?